| | South Lyon, MI | Chelsea, MI | United States |
| Population | 11,786 | 5,447 | 329,725,481 |
| Female Population | 53.4% | 54.3% | 50.5% |
| Male Population | 46.6% | 45.8% | 49.5% |
| Median Age | 43.8 | 48.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 11,327 | 4,951 | 309,327,143 |
| Population - 2000 | 10,036 | 4,398 | 285,036,114 |
| Population - 1990 | 5,857 | 3,772 | 251,960,433 |
| Pop. 2000 to Now | 18.0% | 22.3% | 15.6% |
| Pop. 1990 to Now | 102.3% | 42.6% | 30.8% |
| space4 | | | |
| Population Density | 3,150.5 | 1,506.4 | 93.4 |
| Land Area | 3.7 | 3.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | South Lyon, MI | Chelsea, MI | United States |
| Age 0 to 4 | 4.5% | 4.4% | 5.9% |
| Age 5 to 9 | 6.4% | 6.9% | 6.1% |
| Age 10 to 14 | 6.3% | 3.4% | 6.6% |
| Age 15 to 17 | 3.3% | 3.7% | 3.9% |
| Age 18 to 20 | 4.0% | 5.0% | 4.0% |
| Age 21 to 24 | 6.2% | 0.9% | 5.2% |
| Age 25 to 34 | 9.2% | 9.8% | 13.8% |
| Age 35 to 44 | 11.4% | 11.1% | 12.9% |
| Age 45 to 54 | 13.8% | 11.6% | 12.6% |
| Age 55 to 59 | 9.1% | 4.5% | 6.7% |
| Age 60 to 64 | 9.0% | 7.8% | 6.3% |
| Age 65 to 74 | 9.4% | 12.5% | 9.6% |
| Age 75 to 84 | 5.8% | 11.6% | 4.5% |
| Age 85 and over | 1.6% | 6.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | South Lyon, MI | Chelsea, MI | United States |
| White | 89.9% | 95.6% | 59.4% |
| Black | 0.6% | 0.8% | 12.2% |
| Asian | 2.8% | 0.1% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 4.1% | 1.9% | 3.2% |
| Hispanic | 2.7% | 1.6% | 18.4% |
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| Marriage & Family | | | |
| | South Lyon, MI | Chelsea, MI | United States |
| Married Population | 53.9% | 56.7% | 49.8% |
| Currently Married | 53.3% | 52.8% | 48.0% |
| Married but Separated | 0.6% | 3.9% | 1.8% |
| Single Population | 46.1% | 43.3% | 50.2% |
| Never Married | 25.9% | 18.8% | 33.8% |
| Divorced | 14.1% | 10.3% | 10.8% |
| Widowed | 6.1% | 14.3% | 5.6% |
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| Household Size | 2.31 | 2.07 | 2.60 |
| Households | 5,074 | 2,571 | 124,010,992 |
| Family Households | 3,170 | 1,348 | 80,755,759 |
| Married couple, w/children | 29.4% | 35.8% | 30.5% |
| Married couple, no children | 49.8% | 53.3% | 42.9% |
| Non Family Households | 1,904 | 1,223 | 43,255,233 |
| Single householder, w/children | 13.4% | 7.5% | 15.8% |
| Single householder, no children | 7.4% | 3.4% | 10.8% |